Add some specific project properties and add an example post

After my discussion with @dlech, I went ahead and implemented the properties that we had discussed. In total, I added and implemented 5 properties:
- `github_repo`: A link to a GitHub repo with the project's code (would allow future GitHub integration if we wanted it)
- `code_url`: A generic fallback URL if no GitHub repo is provided
- `homepage`: A pretty webpage for the project (people probably won't have one, but just in case they do...)
- `youtube_video` and `youtube_video_pre` A YouTube video hash and associated description text to be inserted before the post content

I added a right rail on the project page that holds this info, along with user cards for the authors of the post (they aren't official cards, but they might as well be; they look good). My example post is in the posts folder, but I set the unpublished property so that it doesn't appear on the site.

Once I implement any feedback that I get and this code is merged, I can submit a Wiki page and associated link on submitting posts.

There are also a few other features that I want to implement later (such as attachments), but I'm going to wait until this first wave is resolved.